Name

Operating systems using the
systemd(1)
system and service manager are organized based on a file system
hierarchy inspired by UNIX, more specifically the hierarchy
described in the File
System Hierarchy specification and
hier(7).
This manual page describes a more minimal, modernized subset of
these specifications that defines more strictly the suggestions
and restrictions systemd makes on the file system
hierarchy.

Many of the paths described here are queriable
with the
systemd-path(1)
tool.

The boot partition used for bringing up the
system. On EFI systems this is possibly the EFI System
Partition, also see
systemd-gpt-auto-generator(8).
This directory is usually strictly local to the host, and
should be considered read-only, except when a new kernel or
boot loader is installed. This directory only exists on
systems that run on physical or emulated hardware that
requires boot loaders.

System-specific configuration. This directory
may or may not be read-only. Frequently, this directory is
pre-populated with vendor-supplied configuration files, but
applications should not make assumptions about this directory
being fully populated or populated at all, and should fall
back to defaults if configuration is
missing.

The location for normal user's home
directories. Possibly shared with other systems, and never
read-only. This directory should only be used for normal
users, never for system users. This directory and possibly the
directories contained within it might only become available or
writable in late boot or even only after user authentication.
This directory might be placed on limited-functionality
network file systems, hence applications should not assume the
full set of file API is available on this directory.
Applications should generally not reference this directory
directly, but via the per-user $HOME
environment variable, or via the home directory field of the
user database.

The place to store general server payload,
managed by the administrator. No restrictions are made how
this directory is organized internally. Generally writable,
and possibly shared among systems. This directory might become
available or writable only very late during
boot.

The place for small temporary files. This
directory is usually mounted as a "tmpfs"
instance, and should hence not be used for larger files. (Use
/var/tmp for larger files.) Since the
directory is accessible to other users of the system it is
essential that this directory is only written to with the
mkstemp(3),
mkdtemp(3)
and related calls. This directory is usually flushed at
boot-up. Also, files that are not accessed within a certain
time are usually automatically deleted. If applications find
the environment variable $TMPDIR set they
should prefer using the directory specified in it over
directly referencing /tmp (see
environ(7)
and
IEEE
Std 1003.1 for details).

Contains per-user runtime directories, each
usually individually mounted "tmpfs"
instances. Always writable, flushed at each reboot and when
the user logs out. User code should not reference this
directory directly, but via the
$XDG_RUNTIME_DIR environment variable, as
documented in the XDG
Base Directory Specification.

Vendor-supplied operating system resources.
Usually read-only, but this is not required. Possibly shared
between multiple hosts. This directory should not be modified
by the administrator, except when installing or removing
vendor-supplied packages.

Binaries and executables for user commands,
that shall appear in the $PATH search path.
It is recommended not to place binaries in this directory that
are not useful for invocation from a shell (such as daemon
binaries); these should be placed in a subdirectory of
/usr/lib instead.

Static, private vendor data that is compatible
with all architectures (though not necessarily
architecture-independent). Note that this includes internal
executables or other binaries that are not regularly invoked
from a shell. Such binaries may be for any architecture
supported by the system. Do not place public libraries in this
directory, use $libdir (see below),
instead.

Location for placing dynamic libraries, also
called $libdir. The architecture identifier
to use is defined on Multiarch
Architecture Specifiers (Tuples) list. Legacy
locations of $libdir are
/usr/lib,
/usr/lib64. This directory should not be
used for package-specific data, unless this data is
architecture-dependent, too. To query
$libdir for the primary architecture of the
system, invoke:

Resources shared between multiple packages,
such as documentation, man pages, time zone information, fonts
and other resources. Usually, the precise location and format
of files stored below this directory is subject to
specifications that ensure interoperability.

Repository for vendor-supplied default
configuration files. This directory should be populated with
pristine vendor versions of all configuration files that may
be placed in /etc. This is useful to
compare the local configuration of a system with vendor
defaults and to populate the local configuration with
defaults.

Persistent, variable system data. Must be
writable. This directory might be pre-populated with
vendor-supplied data, but applications should be able to
reconstruct necessary files and directories in this
subhierarchy should they be missing, as the system might start
up without this directory being populated. Persistency is
recommended, but optional, to support ephemeral systems. This
directory might become available or writable only very late
during boot. Components that are required to operate during
early boot hence shall not unconditionally rely on this
directory.

Persistent system cache data. System
components may place non-essential data in this directory.
Flushing this directory should have no effect on operation of
programs, except for increased runtimes necessary to rebuild
these caches.

The place for larger and persistent temporary
files. In contrast to /tmp this directory
is usually mounted from a persistent physical file system and
can thus accept larger files. (Use /tmp
for smaller files.) This directory is generally not flushed at
boot-up, but time-based cleanup of files that have not been
accessed for a certain time is applied. The same security
restrictions as with /tmp apply, and
hence only
mkstemp(3),
mkdtemp(3)
or similar calls should be used to make use of this directory.
If applications find the environment variable
$TMPDIR set they should prefer using the
directory specified in it over directly referencing
/var/tmp (see
environ(7)
for details).

The root directory for device nodes. Usually
this directory is mounted as a "devtmpfs"
instance, but might be of a different type in
sandboxed/containerized setups. This directory is managed
jointly by the kernel and
systemd-udevd(8),
and should not be written to by other components. A number of
special purpose virtual file systems might be mounted below
this directory.

Place for POSIX shared memory segments, as
created via
shm_open(3).
This directory is flushed on boot, and is a
"tmpfs" file system. Since all users have
write access to this directory, special care should be taken
to avoid name clashes and vulnerabilities. For normal users,
shared memory segments in this directory are usually deleted
when the user logs out. Usually it is a better idea to use
memory mapped files in /run (for system
programs) or $XDG_RUNTIME_DIR (for user
programs) instead of POSIX shared memory segments, since those
directories are not world-writable and hence not vulnerable to
security-sensitive name clashes.

A virtual kernel file system exposing the
process list and other functionality. This file system is
mostly an API to interface with the kernel and not a place
where normal files may be stored. For details, see
proc(5).
A number of special purpose virtual file systems might be
mounted below this directory.

A hierarchy below /proc
that exposes a number of kernel tunables. The primary way to
configure the settings in this API file tree is via
sysctl.d(5)
files. In sandboxed/containerized setups this directory is
generally mounted read-only.

A virtual kernel file system exposing
discovered devices and other functionality. This file system
is mostly an API to interface with the kernel and not a place
where normal files may be stored. In sandboxed/containerized
setups this directory is generally mounted read-only. A number
of special purpose virtual file systems might be mounted below
this directory.

On some architecture ABIs this compatibility
symlink points to $libdir, ensuring that
binaries referencing this legacy path correctly find their
dynamic loader. This symlink only exists on architectures
whose ABI places the dynamic loader in this
path.

User applications may want to place files and directories in
the user's home directory. They should follow the following basic
structure. Note that some of these directories are also
standardized (though more weakly) by the XDG
Base Directory Specification. Additional locations for
high-level user resources are defined by xdg-user-dirs.

Persistent user cache data. User programs may
place non-essential data in this directory. Flushing this
directory should have no effect on operation of programs,
except for increased runtimes necessary to rebuild these
caches. If an application finds
$XDG_CACHE_HOME set is should use the
directory specified in it instead of this
directory.

Application configuration and state. When a
new user is created this directory will be empty or not exist
at all. Applications should fall back to defaults should their
configuration or state in this directory be missing. If an
application finds $XDG_CONFIG_HOME set is
should use the directory specified in it instead of this
directory.

Executables that shall appear in the user's
$PATH search path. It is recommended not to
place executables in this directory that are not useful for
invocation from a shell; these should be placed in a
subdirectory of ~/.local/lib instead.
Care should be taken when placing architecture-dependent
binaries in this place which might be problematic if the home
directory is shared between multiple hosts with different
architectures.

Resources shared between multiple packages,
such as fonts or artwork. Usually, the precise location and
format of files stored below this directory is subject to
specifications that ensure interoperability. If an application
finds $XDG_DATA_HOME set is should use the
directory specified in it instead of this
directory.

Unprivileged processes generally lack write access to most
of the hierarchy.

The exceptions for normal users are
/tmp,
/var/tmp,
/dev/shm, as well as the home directory
$HOME (usually found below
/home) and the runtime directory
$XDG_RUNTIME_DIR (found below
/run/user) of the user, which are all
writable.

For unprivileged system processes only
/tmp,
/var/tmp and
/dev/shm are writable. If an
unprivileged system process needs a private, writable directory in
/var or /run, it is
recommended to either create it before dropping privileges in the
daemon code, to create it via
tmpfiles.d(5)
fragments during boot, or via the
RuntimeDirectory= directive of service units
(see
systemd.unit(5)
for details).

Unix file systems support different types of file nodes,
including regular files, directories, symlinks, character and
block device nodes, sockets and FIFOs.

It is strongly recommended that /dev is
the only location below which device nodes shall be placed.
Similar, /run shall be the only location to
place sockets and FIFOs. Regular files, directories and symlinks
may be used in all directories.

Developers of system packages should follow strict rules
when placing their own files in the file system. The following
table lists recommended locations for specific types of files
supplied by the vendor.

Table 1. System Package Vendor Files Locations

Directory

Purpose

/usr/bin

Package executables that shall appear in the $PATH executable search path, compiled for any of the supported architectures compatible with the operating system. It is not recommended to place internal binaries or binaries that are not commonly invoked from the shell in this directory, such as daemon binaries. As this directory is shared with most other packages of the system special care should be taken to pick unique names for files placed here, that are unlikely to clash with other package's files.

/usr/lib/arch-id

Public shared libraries of the package. As above, be careful with using too generic names, and pick unique names for your libraries to place here to avoid name clashes.

/usr/lib/package

Private, static vendor resources of the package, including private binaries and libraries, or any other kind of read-only vendor data.

/usr/lib/arch-id/package

Private other vendor resources of the package that are architecture-specific and cannot be shared between architectures. Note that this generally does not include private executables since binaries of a specific architecture may be freely invoked from any other supported system architecture.

/usr/include/package

Public C/C++ APIs of public shared libraries of the package.

Additional static vendor files may be installed in the
/usr/share hierarchy, to the locations
defined by the various relevant specifications.

During runtime and for local configuration and state
additional directories are defined:

Table 2. System Package Variable Files Locations

Directory

Purpose

/etc/package

System-specific configuration for the package. It is recommended to default to safe fallbacks if this configuration is missing, if this is possible. Alternatively, a tmpfiles.d(5) fragment may be used to copy or symlink the necessary files and directories from /usr/share/factory during boot, via the "L" or "C" directives.

/run/package

Runtime data for the package. Packages must be able to create the necessary subdirectories in this tree on their own, since the directory is flushed automatically on boot. Alternatively, a tmpfiles.d(5) fragment may be used to create the necessary directories during boot. Alternatively, the RuntimeDirectory= directive of service units may be used (see systemd.unit(5) for details.)

/run/log/package

Runtime log data for the package. As above, the package needs to make sure to create this directory if necessary, as it will be flushed on every boot.

/var/cache/package

Persistent cache data of the package. If this directory is flushed the application should work correctly on next invocation, though possibly slowed down due to the need to rebuild any local cache files. The application must be capable of recreating this directory should it be missing and necessary.

/var/lib/package

Persistent private data of the package. This is the primary place to put persistent data that does not fall into the other categories listed. Packages should be able to create the necessary subdirectories in this tree on their own, since the directory might be missing on boot. Alternatively, a tmpfiles.d(5) fragment may be used to create the necessary directories during boot.

/var/log/package

Persistent log data of the package. As above, the package should make sure to create this directory if necessary, as it might be missing.

/var/spool/package

Persistent spool/queue data of the package. As above, the package should make sure to create this directory if necessary, as it might be missing.

Programs running in user context should follow strict rules
when placing their own files in the user's home directory. The
following table lists recommended locations in the home directory
for specific types of files supplied by the vendor if the
application is installed in the home directory. (Note however,
that user applications installed system-wide should follow the
rules outlined above regarding placing vendor files.)

Table 3. User Package Vendor File Locations

Directory

Purpose

~/.local/bin

Package executables that shall appear in the $PATH executable search path. It is not recommended to place internal executables or executables that are not commonly invoked from the shell in this directory, such as daemon executables. As this directory is shared with most other packages of the user special care should be taken to pick unique names for files placed here, that are unlikely to clash with other package's files.

~/.local/lib/arch-id

Public shared libraries of the package. As above, be careful with using too generic names, and pick unique names for your libraries to place here to avoid name clashes.

~/.local/lib/package

Private, static vendor resources of the package, compatible with any architecture, or any other kind of read-only vendor data.

~/.local/lib/arch-id/package

Private other vendor resources of the package that are architecture-specific and cannot be shared between architectures.

Additional static vendor files may be installed in the
~/.local/share hierarchy, to the locations
defined by the various relevant specifications.

During runtime and for local configuration and state
additional directories are defined:

Table 4. User Package Variable File Locations

Directory

Purpose

~/.config/package

User-specific configuration and state for the package. It is required to default to safe fallbacks if this configuration is missing.

$XDG_RUNTIME_DIR/package

User runtime data for the package.

~/.cache/package

Persistent cache data of the package. If this directory is flushed the application should work correctly on next invocation, though possibly slowed down due to the need to rebuild any local cache files. The application must be capable of recreating this directory should it be missing and necessary.